Cooling apparatus

ABSTRACT

Cooling apparatus for use on a vehicle. The apparatus includes a heat exchanger in which heat is removed from a heat load by a coolant, and first and second coolant supplies. The first coolant supply is adapted to receive a first coolant and to supply the first coolant to the heat exchanger. The first coolant is available during normal vehicle operations. The second coolant supply is adapted to receive a second coolant and to supply the second coolant to the heat exchanger. The second coolant is supplied by a fluid supply and is unavailable during normal vehicle operation.

CROSS REFERENCE TO RELATED APPLICATION

This application is a national phase based on PCT application No.PCT/GB01/05230 filed Nov. 27, 2001 Priority is claimed to United Kingdompatent application Ser. No. 0029194.8 filed Nov. 30, 2000

DESCRIPTION OF INVENTION

This invention relates to a cooling apparatus, for example for use in anaircraft avionics pod.

An avionics pod is an aerodynamically shaped container which is mountedon the underside of an aircraft, and which typically contains sensitiveoptical and electronic equipment such as navigation and thermal imagingequipment. The electronic equipment within the pod generates heat, andit is necessary to cool the interior of the pod, to ensure optimumperformance of the optical and electronic equipment.

It is known to cool the pod using “ram air”, i.e. using air pressurisedby the forward speed of the aircraft. Where the ram air is sufficientlycold, for example, if the aircraft is flying at a high altitude, the ramair is typically directed into a heat exchanger, which cools a coolantfluid for the electronic equipment. Where the ambient air temperature isnot sufficiently low, or where additional cooling is required, it isknown to direct the ram air into a turbine where the air is expanded,and hence its temperature reduced, before directing the cooled ram airinto the heat exchanger.

One such prior art arrangement is disclosed in U.S. Pat. No. 4,869,071.

Adequate cooling using ram air alone may not be achieved if the aircraftis not in flight, or the engines are not running. In order to provideadequate cooling under these conditions, it is known to provide anelectrically powered fan to draw ambient air into the pod, in order tocool the pod. This requires an additional electrical power source andcontrol system, which in turn generates more heat.

According to a first aspect of the invention, we provide a coolingapparatus for use on a vehicle, the cooling apparatus including a heatexchanger in which heat is removed from a heat load by a coolant,characterised in that the cooling apparatus also includes a first andsecond coolant supply means, the first coolant supply means beingadapted to receive a first coolant and supply the first coolant to theheat exchanger, the first coolant being available during normal vehicleoperation, and the second coolant supply means being adapted to receivea second coolant and supply the second coolant to the heat exchanger,the second coolant being supplied by a fluid supply means, which isunavailable during normal vehicle operation.

Preferably, the cooling apparatus is adapted to cool an aircraftavionics pod.

Thus, by virtue of such a cooling apparatus, a vehicle, or part of avehicle, such as an avionics pod, may be cooled while the vehicle isstationary, or while the vehicle engine(s) is/are not running, withoutthe need for e.g. an electrically powered fan. This eliminates the needfor a further electrical power supply and control means, and reduces thecost and complexity of the cooling system.

Preferably the first coolant is air from the exterior of the vehiclewhich has been pressurised as a result of normal vehicle operation.

Preferably the second coolant is supplied by a fluid supply means at abase to which the vehicle returns, for example where the vehicle is anaircraft, a fluid supply means based on an aircraft carrier. The secondcoolant may be compressed air, which may be supplied from an airaircraft carrier compressor unit. Alternatively, the fluid supply meansmay be a mobile air compressor.

A first cooling means may be provided to cool the first coolant beforeit enters the heat exchanger. A second cooling means may also beprovided to cool the second coolant before it enters the heat exchanger.

Preferably the first and second cooling means each include an expansionmeans which permits the first and second coolant to expand. Theexpansion means may include an expansion turbine. The second coolingmeans may also include a fan which is driven by rotation of the turbineof the second cooling means, and which is adapted to assist in drawingcoolant through the heat exchanger.

An exhaust vent may be provided in the heat exchanger to permit flow ofexhausted coolant out of the heat exchanger, and the exhaust vent may beclosed using a valve, the valve being adapted to open the exhaust ventwhen the coolant pressure inside the heat exchanger exceeds the pressureat the exterior of the heat exchanger by a predetermined amount.

Furthermore, where the invention is applied to an avionics pod, a podexhaust vent is preferably provided in a wall of the pod to permit flowof exhausted coolant out of the pod, the pod exhaust vent being locatedclose to the fan and being closable by a valve which is adapted to openwhen the pressure in the interior of the pod exceeds the pressure at theexterior of the pod by a predetermined amount.

According to a second aspect of the invention, we provide a method ofcooling a heat load in a vehicle using a cooling apparatus, the coolingapparatus including a heat exchanger in which heat is removed from aheat load by a coolant, characterised in that the method includes thesteps of using a first coolant supply means to supply a first coolant tothe heat exchanger when the vehicle is in normal operation, and using asecond coolant supply means to supply a second coolant to the heatexchanger when the vehicle is at rest and the first coolant isunavailable or is unable to provide adequate cooling.

Preferably the method also includes the step of connecting a fluidsupply means to the second coolant supply means, when the vehicle is atrest, such that the fluid supply means may supply the second coolant tothe heat exchanger.

The invention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is a diagrammatic illustration of a cooling system according tothe invention.

FIG. 2 is a diagrammatic illustration of an aircraft with a coolingsystem in accordance with the invention.

Referring now to the FIG. 1, there is represented an avionics pod 10,which is a container containing optical and electronic equipment 11. Theelectronic equipment 11, in use, generates heat, thus providing a heatload 11 which must be cooled to ensure optimum operation of theelectronic equipment. The avionics pod 10 is typically mounted on theunderside of an aircraft 1.

The heat load 11 is cooled using a cooling apparatus 12, which includesa first heat exchanger 13, and three inlet means 14 a, 14 b, 14 cwhereby coolant is supplied to the first heat exchanger 13. The coolantsupplied to the first heat exchanger 13 cools a further coolant, a loadcoolant, which is contained within a closed duct circuit 39 and the loadcoolant may be pumped around the closed duct circuit 39 by one or morepumps P. The load coolant circulates through the first heat exchanger 13and around the heat load 11, and may be a liquid or a gas.

The first heat exchanger 13 includes an exhaust vent 29, which permitsthe flow of exhausted coolant out of the first heat exchanger 13, andwhich is closable by a heat exchanger exhaust valve 30. The heatexchanger exhaust valve 30 may be a clam type flap valve, in which aclosure member is resiliently biased to close the exhaust vent 29. Whenthe pressure exerted on the closure member from inside the first heatexchanger 13 reaches a predetermined value above the pressure outsidethe first heat exchanger 13, the closure member moves to an openposition, which permits coolant to pass from the heat exchanger 13 tothe interior of the pod 10 through the exhaust vent 29.

A first inlet means 15 is provided in a wall of the pod 10 to collectram air during forward flight, and is connected to a ram air inlet 14 aof the first heat exchanger 13, by means of a duct 16 in which a ram airsupply valve 17 is located. The ram air supply valve may for example bea butterfly valve. The first inlet means 15 includes an apertureextending through a wall of the pod 10 and is adapted to receive thefirst coolant, ram air, from the exterior of the pod 10, from an inletI, and direct it via the duct 16 into the first heat exchanger 13.

The first inlet means 15 is also connected to a second heat exchanger19, such that if the ram air supply valve 17 is closed or partiallyclosed, all or a portion of the ram air will pass through the secondheat exchanger 19. The second heat exchanger 19 has a coolant inlet 23,and a coolant vent 25, which are connected via a closed coolant pathwaywithin the heat exchanger 19, thus permitting heat transfer betweencoolant entering through the coolant inlet 23 and ram air entering fromthe first inlet means 15.

An outlet duct 20 is provided from the second heat exchanger 19, whichdirects ram air passing into the second heat exchanger 19 onto a firstexpansion turbine 18. The first expansion turbine 18 is connected on itsoutlet side 18 b to a cooled ram air inlet means 14 b of the first heatexchanger 13 via a duct 21. The duct 21 has a branch 22 which connectsthe duct 21 to the coolant inlet 23 of the second heat exchanger 19. Thebranch 22 contains a ram air cooling valve 24, and opening of the valve24 permits flow of air from the duct 21 back into the second heatexchanger 19. The ram air cooling valve 24 may if desired, be abutterfly valve.

Operation of the ram air supply valve 17 and the ram air cooling valve24 is controlled by an electronic control means C as will be describedin more detail below.

There is a compressor 27 which is mounted on a common drive shaft 26with the first expansion turbine 18, such that rotation of the firstexpansion turbine 18 causes rotation of the compressor 27. Thecompressor 27 has an inlet side 27 a, which draws fluid from theinterior of the pod 10, and an outlet side 27 b, which is connected tothe exterior of the pod 10 via an exhaust duct 28.

A first pod exhaust vent 40, through which exhaust gases may flow out ofthe interior of the pod, is positioned in a wall of the pod 10, close tothe compressor 27, and at a rear end of the pod 10. The first podexhaust vent 40 is closed by a first exhaust valve 41, the first exhaustvalve 41 being a clam type flap valve, in which a closure member, isresiliently biased to close the first pod exhaust vent 40. When thepressure within the pod 10 exceeds the pressure outside the pod 10 by apredetermined amount, the first exhaust valve 41 opens, thus permittingflow of gas from the interior to the exterior of the pod 10.

A second inlet means 31 is provided in the wall of the pod 10, thesecond inlet means 31 including an aperture in the wall of the pod 10,and connection means to connect the second inlet means 31 to a fluidsupply means 36, thus permitting the second inlet means 31 to receivethe second coolant from the fluid supply means 36.

The fluid supply means 36 is ground based, and is available only whenthe aircraft is stationary. The second coolant is compressed air, andthe fluid supply means 36 is for example a mobile air compressor or ahigh pressure air supply line from a compressor, such as may be providedon an aircraft carrier.

There is a second expansion turbine 32 positioned such that thecompressed air entering the second inlet means 31 is directed into aninlet side 32 a of the second expansion turbine 32. An outlet side 32 bof the second expansion turbine 32 is connected via a duct 33 to acompressed air inlet means 14 c of the first heat exchanger 13 so thatexpanded second coolant may be fed to the inlet 14 b of the heatexchanger 13. A non-return valve D is located in the duct 33 in order toprevent backflow of second coolant from the first heat exchanger 13 tothe second inlet means 31.

There is a fan 35 mounted on a common drive shaft with the secondexpansion turbine 32, such that rotation of the second expansion turbine32 causes rotation of the fan 35. An inlet side 35 a of the fan 35 isconnected to a compressed air outlet means 37 of the first heatexchanger 13, through which coolant may flow out of the first heatexchanger, via a duct 34. An outlet side 35 b of the fan 35 is connectedto a fan vent 38 which expels fluid from the fan 35 into the interior ofthe pod 10. A second pod exhaust vent 42, closed with a second exhaustvalve 43, is located in a wall of the pod 10 close to the fan 35, and isconstructed and functions in an identical fashion to the first podexhaust vent 40 and first exhaust valve 41.

The pod exhaust vents 40, 42 are positioned in the wall of the pod 10 soas to avoid the exhausted gases burning or causing discomfort to groundstaff, and to reduce the likelihood of hot exhaust air being drawn backinto and recirculated within the pod 10.

When the vehicle is in normal use, e.g. flying in the case of anaircraft 1, the fluid supply means 36 will be disconnected.

If the ram air at the first inlet means 15 is sufficiently cool, forexample if the aircraft is flying at high altitude, the cooling system12 may be used in “ram air mode”, in which the ram air supply valve 17is in the open position. Ram air, which is at a relatively highpressure, flows through the first inlet means 15 and into the first heatexchanger 13, and cools the load coolant. Circulation of the loadcoolant thus cools the heat load 11.

The flow of ram air increases the pressure within the first heatexchanger 13, until the heat exchanger exhaust valve 30 opens andpermits the ram air to flow out of the heat exchanger 13 through theexhaust vent 29 and into the interior of the pod 10. The pressureincreases in the interior of the pod 10, until the first 41 and/orsecond 43 exhaust valves open and permit the exhaust gas to flow out ofthe pod 10 through the first 40 and/or second 42 pod exhaust vent.

If the aircraft 1 is flying at a lower altitude, at which the ram airtemperature is not sufficiently low to provide adequate cooling, or ifthe heat load is particularly high, such that ram air alone cannotprovide adequate cooling, the cooling system 12 may be used in “aircycle cooling mode”, in which the ram air supply valve 17 is closed orat least partially closed.

If the ram air supply valve 17 is closed, the ram air is constrained toflow through the second heat exchanger 19, and onto the first expansionturbine 18. The air flow onto the first expansion turbine 18 causes itto rotate. The first expansion turbine 18 permits the ram air to expand,and thus the temperature of the ram air decreases. If the valve 24 inthe branch 22 is closed, all the cooled ram air flows along the duct 21into the first heat exchanger 13, and cools the load coolant, which inturn cools the heat load 11.

As when operated in ram air mode, the flow of ram air increases thepressure within the first heat exchanger 13, until the heat exchangerexhaust valve 30 opens and permits the ram air to flow out of the heatexchanger 13 through the exhaust vent 29 and into the interior of thepod 10. In air cycle cooling mode, however, the pressure of the ram airhas been reduced by the first turbine 18, and may not be high enough todrive the air efficiently through the interior of the pod 10 and out ofthe pod exhaust vents 40 or 42.

Rotation of the first expansion turbine 18 causes rotation of thecompressor 27, and the compressor 27 compresses air from the interior ofthe pod 10, which enters the inlet side 27 a of the compressor 27. Thiscauses a reduction in pressure within the pod 10, and both first 41 andsecond 43 exhaust valves close and to seal the pod exhaust vents 40 and42. Air passes through the compressor 27, and flows along the exhaustduct 28, and is ejected from the pod 10.

If the ram air supply valve 17 is only partially closed, some of the ramair flows into the second heat exchanger 19, and is cooled by the firstexpansion turbine 27, before entering the first heat exchanger 13, andsome of the ram air flows directly into the first heat exchanger 13. Theextent to which the ram air supply valve 17 is open is controlled by thecontrol means C and is optimised according to conditions such as heatload temperature, aircraft altitude, and mach number.

In order to control the temperature and pressure of the cooled ram airpassing into the first heat exchanger 13 from the first expansionturbine 18, the ram air cooling valve 24 in the side duct 22 may beopened. In this case, some of the air from the first expansion turbine18 flowing along duct 21 flows along the branch 22, through the coolantinlet 23 and into the second heat exchanger 19.

This cooled ram air flows along the closed coolant pathway within thesecond heat exchanger 19, cools the ram air within the second heatexchanger 19, and flows out through the coolant vent 25 into theinterior of the pod 10.

When the aircraft 1 is not in flight, e.g. is at rest at a base to whichthe aircraft has returned as indicated in FIG. 2, adequate coolingcannot be provided using ram air alone, even if the “air cycle coolingmode” is employed, for example if the aircraft speed is too low toprovide sufficient ram air pressure for effective cooling. Thus thecooling system 12 may be used in “ground cooling mode”.

In ground cooling mode, the ram air supply valve 17 is opened, so thatany air entrained into the first inlet means 15 passes into the firstheat exchanger 13.

A fluid supply means 36, such as a mobile air compressor or a highpressure air supply, is connected to the second inlet means 31.Compressed air flows into the second inlet means 31, and enters theinlet side 32 a of the second expansion turbine 32. Compressed airimpinging on the second expansion turbine 32 causes it to rotate, whichpermits the air fed to the second expansion turbine 32 to expand. Thusthe temperature of the compressed air is reduced.

Rotation of the second expansion turbine 32 also causes the fan 35 torotate, and to draw air out of the first heat exchanger 13 through duct34, reducing the pressure within the heat exchanger 13. This reductionin pressure causes the heat exchanger exhaust valve 30 to close, andtherefore prevents gas from passing through the exhaust vent 29, anddraws cooled compressed air into the heat exchanger 13 from the secondturbine wheel outlet 32 b via duct 33.

The cooled compressed air entering the first heat exchanger 13 cools theload coolant and circulation of the load coolant cools the heat load 11.Thus the heat load within the pod 10 may be cooled when the aircraft isstationary, and when the engines are not running or the engine speed islow, without the use of an electric fan.

The exhaust air drawn out of the first heat exchanger 13 by the fan 35is expelled through the fan vent 38 into the interior of the pod 10.Pressure builds up inside the pod 10, particularly in the region aroundthe fan vent 38, which causes the second valve 43 to open, and exhaustedcoolant to flow out of the pod 10 through the second pod exhaust vent42.

The embodiment described above is by way of example only, and variousmodifications may be made without affecting the scope of the invention.

For example, the invention is not restricted to use in an avionics pod10. It may, for example, be used to cool electronic equipment or anyother heat load, on or in the interior of an aircraft 1. Moreover, theinvention is not restricted for use in an aircraft 1. It may be used onany vehicle where cooling is required, and where a supply of coolant isavailable during normal operation of the vehicle.

It may not necessary to provide expansion turbines to provide extracooling means for the incoming coolant. Either or both the first andsecond supply means may supply ram air or compressed air respectively,directly to the first heat exchanger 13. Similarly, it may not benecessary to provide a second heat exchanger 19.

The fluid supplied by the fluid supply means 36 need not be compressedair. It could be any other gas. The load coolant in the closed circuit39 may be gas or liquid as desired.

An electric fan may be provided in addition to the cooling system 12, toprovide a back-up for use when ground air cooling is required, but whereno fluid supply means 36 is available.

If desired, to provide for fine control over the cooling achieved withinthe pod 10, the control means C may be provided with various inputs andprovide control outputs according to an algorithm.

For example, if desired, temperature sensors may be provided, such asindicated at S1 to sense the temperature of the load coolant in the loadcoolant loop 39 prior to the load coolant cooling the load 11; at S2 forsensing the temperature of the load coolant subsequent to use in coolingthe load 11; S3 to sense the temperature of the ram air entering thecooling system 12. Each of these temperature sensors S1–S3, and anyother temperature sensors to sense e.g. the temperature of the firstcoolant supplied at each of inlets 14 a, 14 b, 14 c to the first heatexchanger 13, may provide respective inputs to the control means C.

Additionally, inputs A relating to aircraft operating conditions mayprovide inputs to the control means C, e.g. relating to operatingconditions such as Mach number and altitude, which data may readily beobtained from the aircraft's 1 own systems.

In response, the control means C may provide appropriate outputs to thepump P in the load coolant loop 39, and to the ram air supply valve 17and the ram air cooling valve 24.

If desired, there may be provided a by-pass loop B in the load coolantloop to enable load coolant to by-pass the first heat exchanger 13, e.g.when heating rather than cooling of the load 11 may be required, tomaintain the temperature within the pod within given parameters. Thusthe control means C may provide control inputs to one or more valves V1,V2 in the load coolant loop 39, so that the proportion of load coolantallowed to by-pass the load 11 may be varied.

If desired there may be provided a weight-on-wheels sensor S5 to sensewhen the aircraft has landed, which sensor may provide an input to thecontrol means C so that for example assisted cooling of the ram airusing the first expansion turbine 18 may be brought into operation uponlanding, in anticipation of the supply of cooling ram air becominginadequate. Of course, when a fluid supply means 36 is connected to thepod 10, this too may be sensed to provide an input to the control meansC, or if no fluid supply means 36 is available, the weight-on-wheelssensor, or a manual input to the control means C may initiate operationof an electrically operated fan to provide on-ground cooling.

In FIG. 1 the control means C is shown mounted within the pod end. Inanother arrangement, the control means C could be mounted externally ofthe pod 10 for example within the aircraft infrastructure. In thatevent, control lines would be required between the control means and thepod to convey input/output signals.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

1. A cooling apparatus for use on a vehicle, the cooling apparatusincluding a heat exchanger in which heat is removed from a heat load bya coolant, wherein the cooling apparatus also includes a first andsecond coolant supply means, wherein the first coolant supply means isadapted to receive a first coolant and to supply the first coolant tothe heat exchanger, wherein the first coolant is available during normalvehicle operation, wherein the second coolant supply means is a sourceof compressed air which supplies said compressed air coolant to the heatexchanger, and wherein the second compressed air source coolant isunavailable during normal vehicle operation.
 2. A cooling apparatus asclaimed in claim 1 which is adapted to cool an aircraft avionics pod. 3.A cooling apparatus as claimed in claim 1 wherein the first coolant isair from the exterior of the vehicle which has been pressurized as aresult of normal vehicle operation.
 4. A cooling apparatus as claimed inclaim 1 wherein the second coolant is supplied by a fluid supply meansat a base to which the vehicle returns.
 5. A cooling apparatus asclaimed in claim 4 wherein the vehicle is an aircraft, and the fluidsupply means is based on an aircraft carrier.
 6. A cooling apparatus asclaimed in claim 5 wherein the second coolant is supplied from an airaircraft carrier compressor unit.
 7. A cooling apparatus as claimed inclaim 1 wherein the fluid supply means is a mobile air compressor.
 8. Acooling apparatus as claimed in claim 1 wherein a first cooling means isprovided to cool the first coolant before it enters the heat exchanger.9. A cooling apparatus as claimed in claim 1 wherein a second coolingmeans is provided to cool the second coolant before it enters the heatexchanger.
 10. A cooling apparatus as claimed in claim 8 wherein thefirst cooling means includes an expansion means which permits the firstcoolant to expand.
 11. A cooling apparatus as claimed in claim 9 whereinthe second cooling means includes an expansion means which permits thesecond coolant to expand.
 12. A cooling apparatus as claimed in claim 11wherein the expansion means includes an expansion turbine.
 13. A coolingapparatus as claimed in claim 10 wherein the expansion means includes anexpansion turbine.
 14. A cooling apparatus as claimed in claim 12wherein the second cooling means includes a fan which is driven byrotation of the expansion turbine of the second cooling means, and whichis adapted to assist in drawing coolant through the heat exchanger. 15.A cooling apparatus as claimed in claim 1 wherein an exhaust vent isprovided in the heat exchanger to permit flow of exhausted coolant outof the heat exchanger, and the exhaust vent is closed using a valve, thevalve being adapted to open the exhaust vent when the coolant pressureinside the heat exchanger exceeds the pressure at the exterior of theheat exchanger by a predetermined amount.
 16. A cooling apparatus asclaimed in claim 15 wherein the cooling apparatus is adapted to cool anaircraft avionics pod, and a pod exhaust vent is provided in a wall ofthe pod to permit flow of exhausted coolant out of the pod, the podexhaust vent being located close to the fan and being closable by avalve which is adapted to open when the pressure in the interior of thepod exceeds the pressure at the exterior of the pod by a predeterminedamount.
 17. A method of cooling a heat load in a vehicle using a coolingapparatus, the cooling apparatus including a heat exchanger in whichheat is removed from a heat load by a coolant, wherein the methodincludes the steps of using a first coolant supply means to supply afirst coolant to the heat exchanger when the vehicle is in normaloperation not at rest, and using a second coolant supply means to supplya compressed air second coolant to the heat exchanger when the vehicleis at rest and the first coolant is unavailable or is unable to provideadequate cooling.
 18. A method as claimed in claim 17 wherein the methodincludes the step of connecting a fluid supply means to the secondcoolant supply means, when the vehicle is at rest, such that the fluidsupply means may supply the second coolant to the heat exchanger.